1. Field of the Invention
The present invention relates to a jack, and more particularly to a hydraulic jack that can adjust the lift capacity to lift quickly and lower slowly.
2. Description of Related Art
A conventional jack includes a lift arm and a handle mounted on a movable base seat. A hydraulic driver is mounted on the base seat and has a base member with a compound path. A container to hold hydraulic fluid, a release valve and a drive piston to drive a lift arm are mounted on the-base member. The conventional jack employs hydraulic power to extend the drive piston which has a lift arm connected to the distal end. The lift arm can engage an object such as the frame of a car, so that the lift arm can lift the object by extending the lifting piston.
However, the lift capacity of the conventional hydraulic jack is fixed so that the user must choose a jack suitable for the weight of the object to be lifted. Consequently, a jack may not be able to lift an object because of inadequate lift capacity or lifts a light object too slowly due to excessive lift capacity.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional hydraulic jack.